While there are certainly outliers, the OP is making a different point, and I’ll see if I can align it with yours. von Neumann was primarily active in mathemat

While there are certainly outliers, the OP is making a different point, and I’ll see if I can align it with yours. von Neumann was primarily active in mathematics and physics. He published 150 papers. He moved subfields but he did so on timescales of years. He too could only dwell in a place or two at a time; he was skilled and fortunate to be able to move between dwelling places over a career that spanned decades. Polymaths are primarily declared polymaths only at the end of a career with the benefit of hindsight. At any given moment they are temporary specialists.